The applicant's own previously published patent document such as WO01/50176, WO02/46825, WO02/103816 and WO03/104872 constitute a useful source of prior art document. These show, for example, piezoelectric actuator fingers used for driving the displacement of collimators in direct collimator to collimator optical switching. WO02/103816 in particular shows detailed configurations of piezoelectric actuators of a monolithic type. WO03/104872 shows in detail how flexure arrangements may be used to amplify the deflection of an optical element such as a collimator.
Other prior art documents show devices for spreading light from a fibre into different frequency components via a diffraction grating which rely on the modulation of the intensity of each component using either liquid crystal display (LCD) arrays or linear arrays of tilting mirror elements which directly re-image the spectrum from the diffraction grating into another fibre. U.S. Pat. No. 6,661,948 (Capella Photonics Incorporated) uses a diffraction grating and an array of micro-mirrors which are individually and continuously controllable. Such systems rely on so-called micro-electro-mechanical (MEMs) systems. Other similar publications exist such as: U.S. Pat. Nos. 6,695,457, 6,687,431, 6,625,346, 6,549,699, 6,507,685, 6,504,976 and US2002/0131698. Similarly, U.S. Pat. No. 6,535,311 (Corning Incorporated) also relies on the use of MEMs systems which in this publication takes the form of a shutter array. Furthermore, U.S. Pat. No. 6,711,316 (JDS Uniphase Incorporated) also relies on the use of deflector arrays, either liquid crystal, phase arrays or reflective MEMS arrays. This is also the case for patent document U.S. Pat. No. 6,707,959 (JDS Uniphase Incorporated) which relies on the use of MEMS. U.S. Pat. No. 6,204,946 (Lucent Technologies Incorporated) also requires the use of MEMs for receiving multiple-wavelength signals and selectively switching between a transmission mode and a reflection mode.
Another piece of prior art is disclosed in U.S. Pat. No. 6,661,953 (Avanex Corporation). This document shows an apparatus with at least one input fibre; a lens optically coupled to at least one input fibre; a diffraction grating selectively coupled to the lens at a side opposite to at least one input fibre; at least one output fibre optically coupled to the lens at the side opposite to the diffraction grating and a plurality of moveable rods residing at the side of the lens opposite to the diffraction grating, wherein the plurality of moveable rods is capable of intercepting a variable portion of a light traversing through the lens. Whilst this document mentions that their moveable rod array may be fabricated as a micro-electro-mechanical system, it may also be fabricated as a set of bendable piezoelectric rods. The system shown however envisages only inputs/outputs from optical fibres; shows the use of a simple piezoelectric comb without any reflective elements and is concerned primarily with optical detection or attenuation of wavelength channels.